The use of microwave dielectrometers in the mid-range area between the microwave nearfield and farfield has many attractive attributes in relation to scanning human subjects for the presence of contraband, explosives, weapons, and other forms of non-physiologic objects and materials. These virtues are adequately described in various ones of the above-referenced documents.
In a setting such as those described in the above-referenced '388 and '183 patent applications, wherein each one of plural transmission/reception (TR) elements is employed, with each element effectively being responsible for scanning and interrogating a particular, differentiated volume of space in front of it, and recognizing that effectively there is always a “load” in front of each such element, there are circumstances wherein unwanted noise signals significantly degrade the signal-to-noise ratio characteristic of received signals, and do so in a manner which makes assessment of important scanning information difficult segregate and assess. Where any effort is sought to utilize received-signal information in a manner intended to aid in characterizing a “found non-physiologic anomaly”, a noise-induced degradation in signal-to-noise ratio, as just mentioned, can make such a characterization extremely difficult.
I have discovered, however, that there is a very special resolution to this issue, and in particular, a resolution which both solves effectively the signal-to-noise ratio problem, and at the same time does so in a context which preserves all of the key operating and utility advantages of the basic scanning structure and methodology described in the two just-mentioned above-referenced patent applications. My resolution to this issue is grounded in the recognition that collectively, each single TR element, in association with any downstream irradiated load, and the intervening media, form a transmission line in space. As a load is moved toward such a TR element, detected incident reflection-pulse amplitude is seen to increase and decrease in quarter-wavelength spatial intervals, finally disappearing in the farfield where the “load” is not close enough to the TR element to “create” such detectable amplitude variations. This increase and decrease phenomenon is caused by the load-reflected wave alternately being in-phase and out-of-phase with the incident wave with motion in the time or range domains.
The explanation for these changes in a radiating system is well documented in transmission-line theory, and is based upon the output impedances of the transmitting source, of the intervening media, and of the terminating, irradiated load. When all of these are equal, there are no standing waves, and the range or distance from transmitting element (TR element) to load has no appreciable affect on the amplitude of a detected signal. In this situation, a system is said to be terminated in its characteristic impedance.
Changes in terminating load impedance, however, unbalance a system and in fact create standing waves that are detectable. Quantities known in the art as Reflection Coefficient and Standing Wave Ratio are the resulting measurements of this mismatch, or imbalance.
The peak-to-peak (high-to-low) standing-wave values are fairly constant over a wavelength range of about two to about ten wavelengths measured from the transmitting element. If the transmitting element can be moved one-half wavelength relative to a subject being irradiated and scanned, one can, within the mentioned two to ten wavelength range, definitely detect and capture one maximum and one minimum standing-wave peak, regardless of the subject's distance from the transmitting element. Significantly, while these maximum and minimum values will change in the presence of noise, the difference between them will not appreciably change. If a detection system produces a value equal to the peak-to-peak value difference between the maximum and minimum standing-wave peaks, the changes associated with true pulse peak amplitude values are common-moded, thus increasing signal-to-noise ratio.
As will be seen, the apparatus and methodology of the present invention utilizes this detectable maximum-to-minimum standing-wave peak value phenomenon.
In general terms, the present invention relates to microwave dielectometry apparatus, and in particular to such apparatus which includes one (or plural) transmission/reception (TR) element(s), each having a TR axis (the element's operational axis), which element(s) is(are) employable in and with respect to a methodology involving dielectric microwave scanning of a human subject. Further, the invention pertains to such apparatus, and to associated scanning methodology, wherein scanning is done both for the purpose of detecting, in relation to baseline physiologic response data, and according to defined screening criteria, notable differences, or anomalies, in relation to a given individual's “dielectric signature”, and additionally for providing some discernible information regarding the natures of certain forbidden, illegal, dangerous, contraband, etc., non-physiologic objects or material(s) carried on and by a person.
The present invention represents an augmented version of the invention described in the above-identified '183, currently pending patent application—augmented by the introduction and use of an important discovery that by producing relative motion of a TR element along its axis toward/away from an individual being screened, or scanned, and during such scanning (as will be described below), valuable information can be gathered to indicate not only the presences, but also the natures, of certain “forbidden” objects and other non-physiologic materials.
While there are many substance-scanning (or screening) applications in which the TR-element structure, system and methodology of this invention find substantial practical utility, two specific such applications are particularly noted herein, and one of these is employed as a principal model for discussing and explaining the structure and operation (methodology) of this invention. These two applications include (a) security detection, or scanning (screening), at locations such as airports for the purpose of detecting weapons, contraband, etc., and (b) authorized access control for personnel in sensitive areas, for example, in relation to research and development areas within a business. Many other useful applications will come to mind to those generally skilled in the art.
A preferred embodiment of, and manner of practicing, the present invention are described herein in relation to a scanning system and its apparatus which departs from, and offers certain improvements over, a like, predecessor system and methodology that are fully illustrated and described in above-mentioned U.S. Pat. No. 6,057,761. These improvements, which exist in certain areas that involve both mechanical and electrical aspects of the previously illustrated scanning process and structure per se, result in the present invention having certain preferential utility in particular applications, such as in applications involving airport-security screening areas, where a very efficient, high throughput of people needs to be accommodated without compromising scanning resolution and effectiveness. In terms of how scanned data is ultimately read (monitored and evaluated based upon the operation of the TR structure of this invention) to detect dielectric anomalies (non-physiologic) that are important to detect, and except as the present invention proposes a unique form of useful relative motion along the operational axis of a TR element between that element and a person being scanned, substantially the same technology which is described in the just-mentioned '761 patent is also employed, for the most part, in the improved apparatus, system and methodology version which are disclosed in this document.
By way of further background, and regarding the dielectric scanning (or screening) process which is implemented by the TR-element structure of the present invention, as a general statement respecting the relevant physics, all materials have what is known as a dielectric constant. This constant is associated with their physical and electrical (electromagnetic and electrostatic) properties. As a consequence, when exposed to different wavelengths and frequencies of microwave radiation, each material produces a reflection reaction, or response, to that radiation, which response, in nature, is uniquely related, among other things, to the particular material's respective dielectric constant. By subjecting a material to controlled, transmitted, microwave energy, it is possible to interpret a material's reflection “response” thereto in terms of its dielectric constant. The term “dielectric signature” is employed herein to refer to this phenomenon.
Where plural, different characters of materials are closely united in a selected volume of space, microwave radiation employed to observe and detect the “dielectric signature” of that “space” will elicit a response which is based upon an averaging phenomenon in relation to the respective dielectric-constant contributions which are made in that space by the respective, different, individual material components. This averaging condition plays an important role in the effectiveness of use of the present invention, and this role is one which the reader will find fully described and discussed in the above-mentioned '761 patent.
In a system and methodology of the type just above generally outlined and suggested, the TR-element structure (or TR structure) of this invention is designed to direct microwave radiation into the human anatomy (at completely innocuous levels regarding any damage threat to tissue, body fluids, or bone) in such a fashion that it will effectively engage a volumetric space within the body wherein there are at least two, different (boundaried) anatomical (known physiologic) materials, each characterized by a different dielectric constant, which materials co-contribute, in the above-mentioned “averaging” manner, to the “effective”, apparent “uniform” (or nominal homogeneous) dielectric constant of the whole space. As is explained by way of background in the '761 patent, by so designing the TR structure of the present invention and its operation to engage the mentioned at-least-two-material volumetric space inside the anatomy, the likelihood that a weapon, or an article of contraband, will, by the nature of its own dielectric constant, and/or its specific configuration and shape, and/or its precise location and/or disposition relative to the human body, “fool” the invention by masquerading as a normal and expectable anatomical normal physiologic constituent, is just about nil. Preferably the “penetration depth” of this internal anatomical space is about 2½ wavelengths of the system operating frequency as measured mechanically in material having the mentioned “normal” dielectric constant.
If and when a foreign, non-physiologic object, such as a weapon, or a contraband object, is borne by a person, for example closely against the outside the body, the presence of this object will, therefore, and does, change the average dielectric constant of the material content of the volume of space (anatomy, of course, included) which is occupied, and will do so in a very non-normal-anatomical, and very detectable, manner, by the mentioned microwave radiation. Definitively, the presence of such non-expected (non-anatomical physiologic) material significantly changes the average value of the effective, average and apparent, uniform, spatial dielectric constant, in accordance with the averaging phenomena just mentioned above, and creates a situation wherein a distinctly different-than-expected dielectric signature appears as a responsive result of microwave scanning transmission in accordance with practice of the invention. This scanning or screening process may be thought of herein as being a practice of substance-scanning differentiation between physiology and non-physiology.
Further describing important distinctions that exist between prior art conventional practice, and practice performed in accordance with the TR structure of the present invention, whereas conventional scanning systems are designed only to look for and “identify” a rather large number of specific objects and materials (substances), the approach taken according to the present invention is two-fold in nature. First, it is based upon examining human physiology for physiologic irregularities/abnormalities which are not expected to be part of the usual human, physiologic, dielectric signature (within a range of course) that essentially all people's bodies are expected to produce. As a consequence of this quite different “first” approach for scanning, the system and methodology practiced by the TR structure of this invention are significantly more efficient, and quicker, in terms of identifying the presences of weaponry, contraband, etc. problem situations. Any out-of-norm physiologic signature which is detected produces an alarm state, which state can be employed to signal the need for security people to take a closer look at what the particular, just-scanned subject involved might have on his or her person.
Secondly, the invention takes advantage of the discovery, mentioned earlier herein, that shifting of the location of a TR element during a scanning phase, along its operational axis, and unidirectionally either toward or away from a person being scanned, can be utilized to detect the peak and valley amplitude values of the microwave-reception standing wave which exists between a functioning TR element and that person. Specifically these values can be discerned if the TR element is so shifted by a distance which is at least equal to, and preferably slightly greater than, one-half the operational wavelength of the TR element. Significantly, looking at these specific peak and valley values implements a common-mode signal-acquisition practice which greatly minimizes the effects which noise can have on proper and useful signal detection. It thus greatly enhances signal-to-noise ratio.
In this systemic and operational setting, the present invention specifically relates both to a unique utilization of a TR element as an individual per se, and to the utilization of plural-TR-element, integrated, modular tile structure (tile) which includes plural, compactly stacked, piggybacked circuit boards (panels), or layer structure, in one of which are homogeneously molded, in a row and column matrix fashion, an array of common-material, microwave TR-element body structures. For the purpose of principal illustration and discussion of the invention herein, the invention is chiefly described in the context of such a tile structure. In such a tile structure, appropriate operational circuitry (referred to as first circuitry) generally described herein, and implementable in numbers of different ways which are well within the skill of those generally skilled in the relevant art, electrically interconnects the circuit boards, and functions to control and “drive” the operations of the TR elements during what are known as scanning phases in simultaneous transmission and reception modes of operation. More specifically, the TR elements in such a tile structure are densely organized to contribute significantly to overall file-structure compactness. The TR elements in a tile are arranged in a defined row-and-column pattern, and when two tiles are brought into appropriate side-by-side adjacency, this pattern forms an appropriate operational pattern continuum across the two tiles. A useful arrangement of the tiles indeed involves organizing plural tiles themselves into a row-and-column array, and such an array has been determined to be quite effective in a structure desired to “scan”, for example, airline boarding passengers.
According to an illustrative manner of utilizing the invention, for example in the setting of an airport, a kiosk-like unit is provided into which a party to be scanned steps through an open, subject entry-way which is defined by a pair of spaced opposing upright panels, each of which carries an array of integrated, self-contained tile structures, or tiles, each including combined, coaxial, microwave TR elements. These two panels effectively define an always open and exposed through-passage through the region called a scanning zone between them, which region is referred to herein as a defined personnel scanning zone. These panels also define what can be thought of herein as being a panel-orientation-determined path for the passage of a person through the scanning zone. A complete scan of a human subject takes place in two stages, or scanning phases, with, in one phase, these panels being located on one set of opposite sides of the body, such as on the left and right sides of a person, and in the other phase, the panels being disposed in a quadrature-related condition (having been rotated, or revolved, ninety-degrees) to perform a second scan which is taken along the two orthogonally related body sides, such as the front and rear sides of the person. Between these two scan orientations, the panels are revolved (as was just noted) through a ninety-degree arc, and in each of the two scanning positions, there is essentially, and importantly, no relative lateral motion which takes place between the panels and the subject standing between them, and thus between the panels and the scanning zone. Thus, during the scan of each single person, the axes of the TR elements transition back and forth between two orthogonally related orientations relative to the scanning zone.
A special processing feature of the illustrated system employing the present invention, with respect to the handling and scanning of large numbers of people, such as must be handled at airport security locations, is that the illustrated system allows for the creation, essentially, of two, generally orthogonally related lines of people waiting to be scanned, with successive people who are scanned entering the scanning zone, one after another, and alternately, from the heads of each of the two orthogonally related lines. A person to be scanned initially faces the scanning zone with a clear (see-through) view into (and through) that zone between the two panels.
With the person in place in the scanning zone, and disposed relatively stationary within that zone, the first scanning phase takes place to examine, sequentially, the laterally opposite sides of that person. This scanning phase is implemented by a special pattern of high-speed energizations (by the first circuitry mentioned above) of tile-borne TR elements organized into arrays as mentioned above.
As will be seen, during each scanning phase, and with respect to each tile, the TR elements therein are shifted as a unit unidirectionally either toward or away from the system scanning zone by a distance which is no less than, and preferably slightly more than, one-half the selected operating wavelength (herein about 2-inches) of the TR elements. How this relative motion is employed to yield useful scanning information will be discussed below.
When such a first scanning phase is completed, structure supporting the two tile-carrying panels rotates, or revolves, these panels through an arc of ninety-degrees, and stops them in the second scanning position relative to the subject, wherein the front and rear sides of the person are similarly scanned, in a second scanning phase, sequentially under a circumstance similar to that just described where the panels, and the subject between them, are again relatively fixed in lateral positions with respect to one another, but wherein relative motion is produced to change the distance between the TR elements in each tile and the scanning zone. In this second scanning phase, the direction of relative motion for the TR elements in each tile is opposite that in which they were moved in the first scanning phase.
The second scanning operation completes the scan process for the single subject now being discussed, whereupon that subject turns a corner to the right or to the left (this is illustrated in the drawings) depending upon which is considered to be the exit side from the scanning zone, and exits through the now-rotated, open (see-through) space between the two panels. The panels with the tiles of this invention are now positioned orthogonally with respect to the positions that they held when the first person just described was to be scanned, and the lead person in the orthogonally related other line of people now enters the scanning zone from the orthogonal location of that other line. Scanning of this next person takes place in much the same fashion just above described, except for the fact that, when the panel structure rotates through an arc of about ninety-degrees to perform the second scan of this “next” person, it effectively counter-rotates back to the position which it initially held in preparation for the previously explained scanning of the first person mentioned above. Scanning data is appropriately computer acquired from all scanning phases (two per person).
From the scanning data which is gathered with respect to each scanned person, that data, by the operation of what is referred to herein as second circuitry, is compared to a “map” or “schedule” of appropriate, physiologic and other, dielectric data relating to someone with a body type, height and weight similar to that of the person specifically being scanned. Any notable, dielectric-signature-related abnormalities will cause an alarm state to be created (as will be later described), which state causes security people, for example, to call the particular subject aside for further and more focused scanning or other inspection. No photographic imagery is developed from any scanning data. Rather, one of the output qualities of scanned data includes the presentation, on a simple wire-form human anatomy shape, of one or more highlighted general anatomic areas that show where a detected abnormality resides. The relative-motion-associated data acquired may be used now, via the operation of the above-mentioned second circuitry, to characterize the natures of found anomalies. This presentation of data is easily readable and assessable with little personnel-interpretive activity required. Output data may also be presented in a somewhat grid-like, or checkerboard-like, field of light and dark patches whose lightnesses and darknesses are interpretable to indicate the presence of a detected dielectric, non-physiologic abnormality. Portions of this scanning process are more fully described in the '761 patent, and in the mentioned, prior-filed patent applications.
Other features and advantages that are offered by the present invention will become more fully apparent as the description which now follows is read in conjunction with the accompanying drawings.